Measuring Temperature Through The Lid

When I first started out with my WSM in 1997, I used a candy thermometer inserted through the lid vent to measure temperature. Candy thermometers work great, cost $10-12, and can be found at hardware stores, cooking supply stores, and in mail-order catalogs. Taylor is a popular brand that you'll find in many stores. These thermometers usually include a metal clip that is used to attach the thermometer to the edge of a pot, but the clip will also suspend the thermometer in the top-most vent hole, as shown in Picture 1.

Another approach is to stick a thermometer through a cork that is inserted into one of the lid vents. Picture 2 shows a Weber #9815 Replacement Thermometer inserted in this fashion. This is the standard thermometer used on Weber Genesis gas grills and is readily available at hardware stores and home centers for about $10.

After a couple of years, I upgraded from a candy thermometer to an industrial-grade bi-metal thermometer. These thermometers are available in a variety of stem lengths, dial sizes, and temperature ranges. They cost $30-40 and can be purchased from suppliers like Ashcroft, Tel-Tru, and Grainger. These are the thermometers you'll see mounted in expensive cookers used at restaurants and barbecue competitions. The stem contains a bi-metal helix that connects to the dial pointer. "bi-metal" refers to the fact that two different types of metal are bonded together, each having a different rate of expansion and contraction. As the temperature fluctuates, the helix rotates within the stem, causing the pointer on the dial to point to the current temperature.

I initially chose the Trend Model 33 thermometer shown in Pictures 3-5. It has a range of 50-550°F, a 3" dial face, and a 6" stem. I drilled out the clip from my original Taylor candy thermometer to accommodate the Trend's larger diameter stem and reshaped it so it clipped under the edge of the top vent, as seen in Picture 5.

After a few more years passed, I took the plunge and drilled through the lid to mount a thermometer. Picture 6 shows how I mounted a Trend Model 33 thermometer with a 4" stem in the lid on the opposite side of the vent. See Mounting A Thermometer for all the details of this process. I switched to a 4" stem at that time so it would not touch meat placed on the top cooking grate.

Another method for measuring temperature through the lid is to hang a probe thermometer through the vent opening. A Polder thermometer is often used for this purpose. The Polder is described in greater detail below.

A less common approach is to insert a thermometer through a hole drilled in the middle cooking section or in the access door. The process for doing this is the same as that discussed on the Mounting A Thermometer page.

One creative approach that does not require drilling is to remove the top nut and bolt from one of the grate brackets and insert a thermometer through the resulting hole.

One potential problem with these approaches is that the thermometer passes through the very hot area at the outside edge of the middle cooking section, where heat flows up and around the water pan. This can result in readings higher than those measured in the middle of the cooking grate or through the lid.

Measuring Temperature At The Cooking Surface

There are a number of ways to measure temperature at the cooking surface. Oven thermometers come in several varieties and are very affordable. The Taylor Classic Oven Guide, shown at the right in Picture 1, uses an alcohol column to measure temperature and is very accurate. It comes highly recommended by Cook's Illustrated magazine in a March/April 2002 comparison of oven thermometers. Dial-type models, like the one shown at the left in Picture 1, use an inexpensive bi-metal coil and tend to be a bit less accurate.

Unfortunately, oven thermometers are not very practical for use in your smoker because you have to remove the lid to check the temperature. That's something you want to avoid during the cooking process so you don't lose heat. They also get covered with smoke and become difficult to read.

Many people use a Polder probe thermometer (or a Polder clone) to measure temperature at the cooking grate. Shown in Picture 2, the Polder consists of a stainless steel probe attached by a long cable to a display unit that sits outside the cooker.

The probe is held above the cooking surface by inserting it all the way through a potato, through a drilled block of wood or a wine cork, or by inserting it between the bones of a slab of ribs or through the corner of a brisket. (A wine cork can be whittled down and stuck into the cooking grate to hold the probe in position.) The probe cable runs under the edge of the lid to the display unit. The lid will not damage the probe cable as long as you're gentle when replacing the lid..

One common trick with a Polder thermometer is to use two different probes with a single display unit. Insert one probe in the meat and another probe through a holder on the cooking grate, then swap the plugs back and forth on the display unit to read each temperature.

The unit also has an alarm you can set to go off when you've achieved your target temperature, as well as a countdown timer. Newer models can be set to alarm at a low temperature reading, alerting you when the fire is beginning to die out. It's a neat gadget, sells for around $30, and is quite popular among BBQers. You can learn more about them on the Resources page and the BBQ Shopping page.

Remote probe thermometers are a more sophisticated version of the Polder thermometer. The Remote Check ET-7 thermometer from Maverick Industries (Picture 3) features two probes that connect to a radio transmitter outside the cooker. The transmitter sends the temperature readings up to 75 feet to a base unit located inside your house. It features timers and temperature alarms like the Polder. The newer Maverick ET-73 dual probe model is available from Amazon.com for about $40. Another manufacturer called NuTemp makes a thermometer that works with up to three remote probe transmitters.

For the person who demands accurate temperature measurements that would make a scientist proud, an instrument-grade thermocouple thermometer is just the ticket. Pictures 4 and 5 show a Fluke Model 52 thermometer and a variety of immersion, piercing, and bead probes available for the unit.

Picture 6 shows a bead probe that is run through the access door and attached to the cooking grate, providing extremely accurate temperature readings. This type of thermometer also works well as a reference for calibrating other thermometers. The Fluke Model 52 costs around $200 and is available at electronics stores that sell test and measurement equipment.

Instant-Read Analog Thermometer

Used commonly in the food service industry, these thermometers are inserted into the meat and give a fairly quick and accurate reading of internal temperature. A protective sleeve is provided for storage, which clips inside your shirt pocket. They are commonly found at hardware stores, cooking supply stores, and better grocery stores, and cost $10-12.

The quality of these units may vary greatly from one manufacturer to another. I prefer the Taylor brand. If Taylor is not available, make sure the unit you buy displays the NSF (National Sanitation Foundation) logo.

The advantages of an analog model are that they're inexpensive and can usually be recalibrated using an adjustment nut on the back of the dial. See Testing Thermometers For Accuracy for details.

The disadvantages are that the small dial face makes the units of measure difficult to read, they have a narrower effective temperature range than most digital models, and you must insert the thermometer about 1-1/2" into the item being measured, which can be difficult with thin meats. They also don't register the temperature as quickly as one might like.

A basic unit costs $15-30 and is purchased at better cooking supply stores. Temperature readings are shown on a digital display, and some units store the last temperature measured. They usually include a protective cover and an on/off switch. To conserve battery power, some models will shut-off automatically if left on by accident.

Again, I've had better experience with Taylor brand (Picture 1) than with others, but look for the NSF logo at a minimum.

The advantages of a digital model are that the display is easy to read, they register temperature quickly, and they have a larger effective temperature range than most analog models. They also measure temperature at the tip, allowing you to take easy measurements in thin meats and shallow liquids.

The disadvantages are that they cannot be recalibrated and their batteries can go dead. Fortunately, most units are very accurate and the batteries last a long, long time. If a digital thermometer is off by a degree or two, you can always compensate by adding or subtracting from your measurements, which isn't too much of an inconvenience.

Picture 2 shows the ThermoWorks Thermapen, the "Cadillac" of instant-read digital thermometers. This commercial food service unit features a big, easy-to-read LCD display, has a needle-like probe that inserts easily into thin cuts of meat, has a range of -50 to 572°F, and registers temperature in a super-fast four seconds. It operates sort of like a pocket knife--fold out the probe from the handle to turn on the unit, take your measurement, then fold the probe back in to turn it off--very cool! The ThermoWorks Thermapen sells for around $80 and can be ordered by calling 801-756-7705.